This invention relates to a device for converting the mechanical energy of wind into electrical energy using piezoelectric materials.
Piezoelectric materials have long been used to convert electrical energy into mechanical energy. Their use to convert mechanical energy into electrical energy has been generally limited to stress transducers such as strain gauges. The use of such materials in converting mechanical energy to electrical power has not been generally known. However, there are a few patents describing such uses of piezoelectric materials such as U.S. Pat. No. 3,350,853 to Schiavone which discloses the use of a piezoelectric crystal in generating electrical power; U.S. Pat. No. 1,884,547 to Bower which shows an electrical system where a piezoelectric element is subjected to torsional movement to generate an electrical power output; U.S. Pat. No. 4,100,630 to Hendel which describes a wave powered electric generator using piezoelectric elements; U.S. Pat. No. 4,317,047 to de Almada which describes another wave power electric generator; and U.S. Pat. No. 3,239,678 to Kolm et al. which describes a piezoelectric power system for use in conjunction with an exhaust system of a jet engine. The Kolm et al. patent describes piezoelectric material mounted inside an exhaust pipe of a jet engine and describes a piezoelectric system mounted outside the exhaust pipe. Acoustical energy generated by the jet engine causes piezoelectric members to vibrate and in doing so to generate electrical power.
The development of piezoelectric polymers in recent years has made it easier to electromechanically couple such materials to fluid movement of water and air, for example. Piezoelectric fans employing a piezoelectric polymer (polyvinylidene fluoride abbreviated as PVF.sub.2) have been developed which convert electrical energy to motion of air. This application is described in an article entitled "High Field Dielectric Loss of PVF.sub.2 and the Electromechanical Conversion Efficiency of a PVF.sub.2 Fan" by Toda in Ferroelectrics (1979), volume 22, pages 919-923.
Furthermore, U.S. Pat. No. 4,404,490 to Taylor et al. shows an apparatus for generating electrical power from waves near the surface of bodies of water. The apparatus described by Taylor et al. uses piezoelectric polymers.
Further, in April, 1982, the inventor of the present invention described a windmill electric generator in which the blades were constructed with a PVF.sub.2 bimorph. A bimorph is comprised of two PVF.sub.2 sheets placed back to back. This fan included a rotor using a bimorph blade which rotated in the wind. Stressing the bimorph blade caused electrical power to be generated. This piezoelectric polymer electric generator was described in a publication reporting the "Proceedings of the 1982 Wind and Solar Energy Technology Conference" and sponsored by the University of Missouri at Columbia, Mo.